U.S. patent application number 11/681995 was filed with the patent office on 2007-11-01 for method and apparatus for shunt for in vivo thermoelectric power system.
This patent application is currently assigned to CARDIAC PACEMAKERS, INC.. Invention is credited to Blair Erbstoeszer, Kristofer J. James.
Application Number | 20070251565 11/681995 |
Document ID | / |
Family ID | 38647185 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070251565 |
Kind Code |
A1 |
Erbstoeszer; Blair ; et
al. |
November 1, 2007 |
METHOD AND APPARATUS FOR SHUNT FOR IN VIVO THERMOELECTRIC POWER
SYSTEM
Abstract
One embodiment of the present subject matter includes an
apparatus with a first housing portion which is thermally
conductive and which has a first case opening; a second housing
portion which is thermally conductive and which has a second case
opening, the second case opening being hermetically sealed to the
first case opening, with the first housing portion and the second
housing portion at least partially defining an interior volume;
cardiac rhythm management electronics disposed in the interior
volume; a thermal shunt disposed in the interior volume; and a
thermoelectric energy converter disposed in the interior volume and
adjacent the thermal shunt, the thermoelectric energy converter
having a first pole and a second pole, with the first pole
thermally connected to the first housing portion, and the second
pole thermally connected to the shunt.
Inventors: |
Erbstoeszer; Blair;
(Kirkland, WA) ; James; Kristofer J.; (Eagan,
MN) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG & WOESSNER, P.A.
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Assignee: |
CARDIAC PACEMAKERS, INC.
ST. PAUL
MN
|
Family ID: |
38647185 |
Appl. No.: |
11/681995 |
Filed: |
March 5, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60745715 |
Apr 26, 2006 |
|
|
|
60745724 |
Apr 26, 2006 |
|
|
|
60745720 |
Apr 26, 2006 |
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Current U.S.
Class: |
136/232 ;
136/230 |
Current CPC
Class: |
H01L 35/30 20130101;
A61N 1/3785 20130101 |
Class at
Publication: |
136/232 ;
136/230 |
International
Class: |
H01L 35/02 20060101
H01L035/02 |
Claims
1. An apparatus, comprising: a sealed, implantable housing having a
first portion and a second portion; a thermal shunt disposed and
sealed in the housing, with the thermal shunt thermally conductive
to the first portion of the sealed, implantable housing; and a
thermoelectric energy converter disposed and sealed in the housing,
the thermoelectric energy converter having a first pole and a
second pole, with the first pole thermally conductive to a second
housing portion, and the second pole thermally conductive to the
thermal shunt.
2. The apparatus of claim 1, wherein the thermal shunt includes
copper.
3. The apparatus of claim 1, wherein the thermal shunt includes a
heat pipe.
4. The apparatus of claim 1, wherein the thermoelectric energy
converter includes thermopiles.
5. The apparatus of claim 1, wherein the shunt includes one or more
beams extending through a capacitor, the capacitor being disposed
in the interior volume.
6. The apparatus of claim 1, wherein the shunt includes one or more
beams extending through a battery, the battery being disposed in
the interior volume.
7. The apparatus of claim 5, wherein the first housing portion
includes titanium.
8. The apparatus of claim 1, wherein the sealed, implantable
housing is hermetically sealed.
9. The apparatus of claim 8, further comprising a thermally
conductive grease disposed between the first pole and the first
housing portion, and further disposed between the second pole and
the thermal shunt.
10. The apparatus of claim 1, wherein the first pole is a hot
pole.
11. The apparatus of claim 10, wherein the second pole is a cold
pole.
12. The apparatus of claim 1, wherein the shunt defines a shunt
interior volume in which a battery is disposed.
13. The apparatus of claim 12, wherein the battery is a secondary
battery, and thermoelectric energy converter is adapted to charge
the battery.
14. The apparatus of claim 12, wherein the thermoelectric energy
converter is disposed in the shunt interior volume.
15. The apparatus of claim 1, wherein the shunt is an anisotropic
composite.
16. The apparatus of claim 15, wherein the anisotropic composite
includes carbon fiber suspended at least partially in a cured
resin.
17. The apparatus of claim 1, wherein the thermoelectric energy
converter is a thin film thermoelectric energy converter.
18. The apparatus of claim 17, wherein the thermoelectric energy
converter is less than 0.100 inches thick.
19. The apparatus of claim 1, wherein the cardiac rhythm management
electronics include a primary battery adapted to power a
defibrillation capacitor.
20. The apparatus of claim 19, wherein the thermoelectric energy
converter is adapted to power pacemaker electronics.
21. The apparatus of claim 1, wherein the cardiac rhythm management
electronics include a secondary battery, and the thermoelectric
energy converter is adapted to power the secondary battery.
22. The apparatus of claim 21, wherein the secondary battery is
adapted to power pacing electronics.
23. The apparatus of claim 22, wherein the secondary battery is
adapted to power a defibrillation capacitor.
24. An apparatus, comprising: thermoelectric energy conversion
means for converting a temperature differential into energy; sealed
housing means for housing the thermoelectric energy conversion
means and cardiac rhythm management electronics; and shunt means
for conducting thermal energy from the sealed housing means to the
thermoelectric energy conversion means.
25. The apparatus of claim 24, wherein the sealed housing means
includes a first housing portion sealed to a second housing
portion, the first and second housing portions defining an interior
volume.
26. The apparatus of claim 25, wherein the thermoelectric energy
conversion means include a thermoelectric energy converter disposed
in the interior volume, the thermoelectric energy converter
including a hot pole and a cold pole, with the hot pole thermally
connected to the first housing portion, and the cold pole thermally
connected to the second housing portion.
27. The apparatus of claim 25, wherein the shunt means includes a
copper shunt positioned between the first housing portion and a
thermoelectric energy converter.
Description
CLAIM OF PRIORITY AND RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C. 119(e)
of U.S. Provisional Patent Application Ser. No. 60/745,715, filed
Apr. 26, 2006, U.S. Provisional Patent Application Ser. No.
60/745,724, filed Apr. 26, 2006, and U.S. Provisional Patent
Application Ser. No. 60/745,720, filed Apr. 26, 2006, the entire
disclosures of which are hereby incorporated by reference in their
entirety. The present application is related to the following
commonly assigned U.S. patent applications which are filed even
date herewith and incorporated herein by reference in their
entirety: "Method and Apparatus for In Vivo Thermoelectric Power
System," Ser. No. ______ (Attorney Docket No. 279.864US1); "Power
Converter for use with Implantable Thermoelectric Generator," Ser.
No. ______ (Attorney Docket No. 279.B92US1).
TECHNICAL FIELD
[0002] This disclosure relates generally to thermoelectric energy
converters, and more particularly to methods and apparatus
regarding a shunt for in vivo thermoelectric power systems.
BACKGROUND
[0003] As electronics become increasingly miniaturized, existing
applications of electronic technology become more space efficient,
and new applications of electronic technology become possible. For
example, self-powered electronic devices continually become smaller
and more space efficient, creating opportunities for new
applications. This trend is demonstrated by implantable medical
devices.
[0004] But self-powered devices could benefit further from
reductions in the sizes of their power sources. Current
applications do not supplement or replace power sources inside
devices with available external energy sources. Energy could be
gathered from external power sources so long as design changes do
not reduce the useable energy available to self-powered devices, or
negatively impact the rate at which energy is available.
[0005] One external energy source available in some applications is
a thermal gradient. The tendency for heat to flow across a thermal
gradient creates opportunities to generate energy. Some devices
have used this phenomenon to generate electricity. But existing
designs are not compatible with the size or power requirements of
some self-powered implantable devices. Thus, what are needed are
new thermoelectric power system designs compatible with these
applications, which can supplement the energy available from
traditional power sources.
SUMMARY
[0006] One embodiment of the present subject matter includes a
hermetically sealed, implantable housing at least partially
defining an interior volume and having a first portion and a second
portion, a thermal shunt disposed in the interior volume and
disposed along a first housing portion, a thin film thermoelectric
energy converter disposed in the interior volume and adjacent the
thermal shunt, the thermoelectric energy converter having a hot and
a cold pole, with the hot pole thermally connected to the second
housing portion, and the cold pole thermally connected to the
shunt, a thermally conductive grease disposed between the first
pole and the first housing portion, and further disposed between
the second pole and the thermal shunt, wherein the thin film
thermoelectric energy converter is adapted to power cardiac rhythm
management electronics which include a primary battery adapted to
power a defibrillation capacitor.
[0007] Another embodiment of the present subject matter includes a
sealed, implantable housing having a first portion and a second
portion, a thermal shunt disposed and sealed in the housing, with
the thermal shunt thermally connected to the first portion of the
sealed, implantable housing and a thermoelectric energy converter
disposed and sealed in the housing, the thermoelectric energy
converter having a first pole and a second pole, with the first
pole thermally connected to a second housing portion, and the
second pole thermally connected to the thermal shunt.
[0008] One embodiment of the present subject matter includes
connecting a thermoelectric energy converter to a device case, such
that a first pole of the thermoelectric energy converter is
thermally connected to a first housing portion, and a second pole
of the thermoelectric energy converter is thermally connected to a
second housing portion, with the connected first and second housing
portions defining an interior volume in which the thermoelectric
energy converter is disposed, connecting the thermoelectric energy
converter to cardiac rhythm management electronics disposed in the
interior volume and powering the cardiac rhythm management
electronics at least partially with the thermoelectric energy
converter.
[0009] Another embodiment of the present subject matter includes a
first cupped housing portion including titanium and having a first
case opening, a second housing portion including titanium and
having a second case opening, the second case opening being
hermetically sealed to the first case opening, with the first
housing portion and the second housing portion at least partially
defining an interior volume, a secondary battery disposed in the
interior volume, a defibrillation capacitor disposed in the
interior volume, cardioverter defibrillator electronics disposed in
the interior volume and a thin film thermoelectric energy converter
disposed in the interior volume, the thermoelectric energy
converter having a hot pole and a cold pole, with the hot pole
thermally connected to the first housing portion, and the cold pole
thermally connected to the second housing portion, wherein the thin
film thermoelectric energy converter is connected to the secondary
battery, the defibrillation capacitor, and the cardioverter
defibrillation electronics, and the cardioverter defibrillation
electronics are adapted to control the conduction of energy between
the thermoelectric energy converter, the secondary battery, and the
defibrillation capacitor.
[0010] One embodiment of the present subject matter includes
thermoelectric energy conversion means for converting a temperature
differential into energy, sealed housing means for housing the
thermoelectric energy conversion means and cardiac rhythm
management electronics and shunt means for conducting thermal
energy from the sealed housing means to the thermoelectric energy
conversion means.
[0011] Several options are contemplated. Embodiments are included
in which the thermal shunt includes copper. Some embodiments are
included in which the thermal shunt includes a heat pipe. In some
embodiments the thermoelectric energy converter includes
thermopiles. Embodiments are included in which the sealed,
implantable housing is hermetically sealed. In some embodiments a
thermally conductive grease is disposed between the first pole and
the first housing portion, and further disposed between the second
pole and the thermal shunt. Some embodiments are included in which
the first pole is a hot pole. In some embodiments the first pole is
a cold pole. Embodiments are included in which the shunt includes
one or more beams extending through a battery, the battery being
disposed in the interior volume. In some embodiments the first
housing portion includes titanium. Some embodiments are included in
which the shunt defines a shunt interior volume in which a battery
is disposed. In some embodiments the battery is a secondary
battery, and thermoelectric energy converter is adapted to charge
the battery. Embodiments are included in which the thermoelectric
energy converter is disposed in the shunt interior volume. In some
embodiments the shunt is an anisotropic composite. Some embodiments
are included in which the anisotropic composite includes carbon
fiber suspended at least partially in a cured resin. In some
embodiments the thermoelectric energy converter is a thin film
thermoelectric energy converter. Embodiments are included in which
the thermoelectric energy converter is less than 0.100 thick. In
some embodiments the cardiac rhythm management electronics include
a primary battery adapted to power a defibrillation capacitor. Some
embodiments are included in which the thermoelectric energy
converter is adapted to power pacemaker electronics. In some
embodiments the cardiac rhythm management electronics include a
secondary battery, and the thermoelectric energy converter is
adapted to power the secondary battery. Embodiments are included in
which the secondary battery is adapted to power pacemaker
electronics. In some embodiments the secondary battery is adapted
to power a defibrillation capacitor.
[0012] This Summary is an overview of some of the teachings of the
present application and not intended to be an exclusive or
exhaustive treatment of the present subject matter. Further details
about the present subject matter are found in the detailed
description and appended claims. Other aspects will be apparent to
persons skilled in the art upon reading and understanding the
following detailed description and viewing the drawings that form a
part thereof, each of which are not to be taken in a limiting
sense. The scope of the present invention is defined by the
appended claims and their legal equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A shows a self-powered device, according to one
embodiment of the present subject matter.
[0014] FIG. 1B shows a side view of the self-powered device of FIG.
1A.
[0015] FIG. 2 shows a cross section of a self-powered device,
according to one embodiment of the present subject matter.
[0016] FIG. 3 shows a side view of a self-powered device, according
to one embodiment of the present subject matter.
[0017] FIG. 4 illustrates a schematic diagram of an apparatus for
converting power from a thermoelectric energy converter, according
to one embodiment of the present subject matter.
[0018] FIG. 5 shows a partial cross section side view of a
self-powered device, according to one embodiment of the present
subject matter.
[0019] FIG. 6 shows a cross section of a thermoelectric energy
converter and additional components disposed in a shunt, according
to one embodiment of the present subject matter.
[0020] FIG. 7 shows a cross section of a shunt and a thermoelectric
energy converter, according to one embodiment of the present
subject matter.
[0021] FIG. 8 is cross section or a self-powered device showing
thermal gradients, according to one embodiment of the present
subject matter.
[0022] FIG. 9 illustrates a schematic diagram of an apparatus for
converting power from a thermoelectric energy converter, according
to one embodiment of the present subject matter.
DETAILED DESCRIPTION
[0023] The following detailed description of the present subject
matter refers to subject matter in the accompanying drawings which
show, by way of illustration, specific aspects and embodiments in
which the present subject matter may be practiced. These
embodiments are described in sufficient detail to enable those
skilled in the art to practice the present subject matter.
References to "an", "one", or "various" embodiments in this
disclosure are not necessarily to the same embodiment, and such
references contemplate more than one embodiment. The following
detailed description is demonstrative and not to be taken in a
limiting sense. The scope of the present subject matter is defined
by the appended claims, along with the full scope of legal
equivalents to which such claims are entitled.
[0024] Thermoelectric devices convert thermal gradients to energy,
and visa versa. These devices include an interface between
dissimilar materials. In some cases the dissimilar materials are
metals. In some instances the dissimilar materials are
semiconductors. Additional materials which demonstrate the Seebeck
effect fall within the present scope.
[0025] Despite the availability of materials which demonstrate the
Seebeck effect, some applications have yet to benefit from
thermoelectric technology. Problems include an inability for some
applications to use available thermal gradients. Additionally, some
existing designs are too large for practical implantation.
[0026] Various embodiments within the scope of the present subject
matter provide a thermoelectric energy conversion system for a
self-powered device. Self-powered devices contemplated by the
present subject matter include implantable devices. Implantable
devices contemplated by the present subject matter include, but are
not limited to, cardiac rhythm management devices, neurostimulation
devices, and other devices not expressly listed herein. In various
embodiments, the thermoelectric energy conversion system of the
present subject matter operates inside an implantable device, using
a thermal gradient present at the implantable device. The
embodiments provide enough energy to power electronics within the
device.
[0027] FIG. 1A shows a self-powered device, according to one
embodiment of the present subject matter. In various embodiments,
the self-powered device is suited for use as an implantable medical
device. In some of these embodiments, the self-powered device is a
cardiac rhythm management device. In additional embodiments, the
device is a neurostimulation device. These are only some of the
self-powered devices contemplated by the present subject matter.
The present subject matter extends to additional devices not
expressly listed herein. This front view shows a header 102, and a
housing 110. In various embodiments, the housing 110 includes
titanium. In additional embodiments, the housing 110 includes
stainless steel. Other materials for the housing 110 which are
compatible with implanting electronics can optionally be used.
[0028] Within housing 110, in some embodiments of the present
subject matter, is a power source 104. Power source 104 includes a
primary battery, in various embodiments. Some embodiments use one
or more lithium ion batteries. Of these, some embodiments use one
or more lithium manganese dioxide batteries. Other known primary
battery compositions are also be used, in various embodiments.
Additionally, power source 104, in various embodiments, includes a
secondary battery. Secondary batteries within the present subject
matter include rechargeable lithium ion types. Other known
secondary batteries are also used. Also, in some embodiments, power
source 104 includes a capacitor. Aluminum electrolytic capacitors
are used in some embodiments of the present subject matter. Other
capacitor compositions additionally fall within the present
scope.
[0029] Power source 104, in various embodiments, could include a
combination of two or more of a primary battery, a secondary
battery, or a capacitor. Power source 104, in various embodiments,
provides a power source which is available for use in concert with
thermoelectric energy converter 106. In various embodiments, power
source 104 is used in applications where a power source is needed
which delivers power at a rate different from a thermoelectric
energy converter. In various embodiments, power source 104 is used
for powering electronics when a thermal gradient is not available.
Embodiments not including power source 104 additionally fall within
the present scope.
[0030] The present subject matter provides a thermoelectric energy
converter 106 inside of housing 110. In various embodiments,
housing 110 includes a first housing portion which is thermally
conductive and which has a first housing opening. Housing 110
additionally includes, in various embodiments, a second housing
portion which is thermally conductive and which has a second
housing opening. In various embodiments, the second housing opening
is hermetically sealed to the first housing opening. In various
embodiments, the first housing portion and the second housing
portion at least partially define an interior volume.
Thermoelectric energy converter 106, in various embodiments, is
disposed in the interior volume.
[0031] Thermoelectric energy converter has a hot pole and a cold
pole. In various embodiments, the hot pole is thermally connected
to the first housing portion. In additional embodiments, the cold
pole is thermally connected to the second housing portion.
Configured as such, the self-powered device demonstrated in the
present embodiment includes within its housing a thermoelectric
energy converter, including the hot pole and the cold pole of the
thermoelectric energy converter.
[0032] Such a configuration is useful to power additional
electronics 108, in various embodiments. In some embodiments,
cardiac rhythm management electronics are disposed in the interior
volume of housing 110. In some embodiments, neurostimulation
electronics are disposed in the interior volume of housing 110.
Other electronics variants not expressly listed herein are
additionally contemplated by the present subject matter. In some
embodiments, the electronics include cardioverter defibrillator
electronics. In some embodiments, the additional electronics 108
are powered solely by the thermoelectric energy converter 106, and
an additional power source 104 is not included in the device.
[0033] In some embodiments, the thermoelectric energy converter 106
is adapted to power pacemaker electronics. In some of these
embodiments, power source 104 is included in the device, but does
not power pacemaker electronics. For example, power source 104 can
provide power for a defibrillation capacitor. In some embodiments
using a thermoelectric energy converter 106 to power pacemaker
electronics, power source 104 is not included.
[0034] In some embodiments, the additional electronics 108 are
powered by both the thermoelectric energy converter 106 and the
power source 104. In various embodiments, the choice of what power
source to use to power additional electronics 108 depends on the
energy rate which should to be available. For example, in some
embodiments, the thermoelectric energy converter produces power at
a rate too low to deliver energy for a defibrillation pulse. In
some of these embodiments, power source 104 includes a capacitor
used to provide a defibrillation pulse to a patient.
[0035] In some embodiments having a power source 104 including a
capacitor, multiple capacitor pulses are needed to treat a patient.
In these situations, some capacitors are not big enough to hold
charge suitable for delivery of multiple pulses. Such housings
require an additional power source which can discharge at a high
rate to charge the capacitor between defibrillation pulses. In
various embodiments, the thermoelectric energy converter 106 cannot
discharge at a high enough rate to charge a capacitor in between
defibrillation pulses. In such embodiments, additional power source
104 includes additional components, such as a battery, to charge
the capacitor at a rate higher than is available from the
thermoelectric energy converter 106. In some embodiments, a primary
battery is used. Additional embodiments use a secondary battery.
Some embodiments use a combination of a primary battery and a
secondary battery.
[0036] The present subject matter enables a smaller battery to be
used to charge a capacitor, in various embodiments. Over the course
of the service life of the self-powered device, a battery/capacitor
combination may be called upon to deliver therapies multiple times,
over multiple episodes. For example, a device may deliver 2 pulses
during an episode, and may encounter one episode per year, for 5
years. Batteries in defibrillators are known to last between 3 and
7 years. To provide energy for multiple episodes, a battery should
be sized to operate sufficiently during multiple episodes. However,
if the battery need only be sized to function appropriately during
one episode, it may be smaller. Battery discharge during the
episode can be replenished using the thermoelectric device, in
various embodiments of the present subject matter.
[0037] To provide useful power, the thermoelectric energy converter
106 should be able to harvest thermal energy from the human body
and convert it into usable power. Various embodiments of the
present subject matter are configured to provide power when a
thermal gradient exists which is between approximately 0.5 degrees
Celsius, and approximately 5.0 degrees Celsius. Some embodiments
provide power using a thermal gradient of approximately 4.3 degrees
Celsius. In some of embodiments, the thermoelectric energy
converter is adapted to produce power when exposed to a thermal
gradient of approximately 0.5 degrees Celsius to approximately 1.5
degrees Celsius. Various embodiments of the present subject matter
are configured such that the thermoelectric energy converter is
adapted to produce from about 5 microwatts when exposed to a
thermal gradient of approximately 0.5 degrees Celsius, to about 80
microwatts when exposed to a thermal gradient of approximately 4.3
degrees Celsius. In some examples, the thermoelectric energy
converter is adapted to produce approximately 30 microwatts when
exposed to a thermal gradient of approximately 1.0 degrees Celsius.
These power production examples are evinced in some of the
configurations contemplated by the present subject matter, but are
not intended to be limiting of the range of configurations
contemplated by the present subject matter. Additionally, the
thermal gradients provided herein, and their relationship to power
production, are those of example embodiments which are illustrative
of the present subject matter, but not demonstrative of the entire
range of configurations contemplated by the present subject
matter.
[0038] Various types of thermoelectric energy converters are used
within the present subject matter. In some embodiments, the
thermoelectric energy converter includes thermopiles. In some
embodiments, the thermoelectric energy converter is a thin film
thermoelectric energy converter. Some thermoelectric energy
converters include a superlattice. Some thermoelectric energy
converters operate using thermotunneling. Other known
thermoelectric designs which meet packaging and power requirements
of implantable self-powered devices additionally fall within the
present scope.
[0039] FIG. 1B shows a side view of the self-powered device of FIG.
1A. Pictured in the view are header 102 and housing 110. The
housing 110 is comprised, in various embodiments, of a first
portion 112 and a second portion 114. In various embodiments, first
portion 112 is cup shaped and includes a first aperture conformed
to a second aperture of the second portion 114, wherein the first
and second apertures are hermetically sealed at seam 150.
[0040] FIG. 2 shows a cross section of a self-powered device 224,
according to one embodiment of the present subject matter. Various
embodiments of the present subject matter include a housing. In
various embodiments, the housing includes a first housing portion
202 and a second housing portion 214. Various embodiments
additionally include electronics 210, an additional power source
212, and a thermoelectric energy converter system 204.
[0041] In some embodiments, the first housing portion 202 is cup
shaped and the second housing portion 214 is cup shaped. In some
examples, the first housing portion and the second housing portion
meet, with respective openings conforming to one another along
plane 222. Although the first housing portion 202 and the second
housing portion 214 of the present subject matter demonstrate such
a configuration, other configurations are possible, including ones
in which first housing portion 202 and second housing portion 214
conform to one another along an irregular interface. In various
embodiments, the first housing portion 202 and the second housing
portion 214 are mechanically connected. Some embodiments are welded
together. In some embodiments, a laser weld joins the first housing
portion 202 and the second housing portion 214.
[0042] In various embodiments of the present subject matter, the
thermoelectric energy converter system 204 is thermally connected
to the first housing portion 202 and the second housing portion
210. For example, some embodiments position a hot pole 218 of a
thermoelectric energy converter system 204 adjacent a first housing
portion 202, such that the hot pole and the first housing portion
are in thermal conduction. In additional embodiments, the cold pole
220 of the thermoelectric energy converter system 204 is positioned
adjacent the second housing portion 214, such that the cold pole
220 and the second housing portion 214 are in thermal
conduction.
[0043] In various embodiments, performance of the thermoelectric
energy conversion system 204 is enhanced due to reduced thermal
conduction between first housing portion 202 and second housing
portion 214. Some embodiments of the present subject matter utilize
materials for the first housing portion 202 and/or the second
housing portion 214 which are less thermally conductive. Some
embodiments, for example, use housing portions constructed of
titanium. Titanium has a thermal conductivity of approximately 17
Watts per meter Kelvin, in various embodiments. Additional
embodiments use housing portions constructed of stainless steel.
Some embodiments of the present subject matter use 3161 stainless
steel. Some embodiments of the present subject matter use a
stainless steel having a thermal conductivity of approximately 16
watts per meter Kelvin. Other materials for the first and/or second
housing portions fall within the present scope.
[0044] In some embodiments, the performance of the thermoelectric
energy conversion system 204 is enhanced by an interconnection
between the first and second housing portions and their respective
connections to the hot and cold pole of the thermoelectric energy
conversion system. For example, connection 216, in various
embodiments, enhances thermal conductivity between second housing
portion 214 and cold pole 220 using a thermally conductive grease.
Other mediums which enhance thermal conductivity are additionally
contemplated, including, but not limited to, epoxy and other
adhesives. In some examples, a thermally conductive grease has a
thermal conductivity of from about 4 Watts per meter Kelvin to
about 5 Watts per meter Kelvin. Additional embodiments weld cold
pole 220 to second housing portion 214. Some embodiments include a
thermally conductive filler material which thermally interconnects
the second housing portion 214 and the cold pole 220. These
configurations for connecting the cold pole 220 and the second
housing portion 214 apply to connections to the first housing
portion 202 and the hot pole 218, in various embodiments.
[0045] In various embodiments, the thermoelectric energy converter
system 204 has a thickness of D1. In some embodiments, the
thermoelectric energy converter is less than the thickness of the
thermoelectric energy converter system. Some embodiments include a
thermoelectric energy converter system 204 which is less than the
thickness D2 of the device 224 in which it is housed. In some
embodiments, the thickness D1 is less than 0.020 inches thick. Some
embodiments are between 0.020 inches and 0.040 inches thick.
Embodiments of the present subject matter are between 0.040 inches
and 0.100 inches thick. Embodiments having a thickness D1 which is
greater than 0.100 inches thick are also contemplated. These
combinations are provided for illustration and are not intended to
be limiting as the present subject matter contemplates thicknesses
which are not listed herein expressly.
[0046] In some embodiments, the connected first housing portion and
second housing portion have a substantially plate shaped exterior.
In some embodiments, the plate shaped exterior has a first planar
surface and a second planar surface, wherein the thermoelectric
energy converter system 204 is plate shaped and is disposed in the
housing such that a thickness of the thermoelectric energy
converter extends away from one of the first planar surface and the
second planar surface.
[0047] In various embodiments, the device 224 is exposed to a
thermal gradient .DELTA.T. In various embodiments, the thermal
gradient .DELTA.T is from about 0.5 degrees Celsius to about 4.3
degrees Celsius. In additional embodiments, the thermal gradient
.DELTA.T is from about 0.5 degrees Celsius to about 1.5 degrees
Celsius. In some embodiments, the thermal gradient .DELTA.T is
about 1.0 degrees Celsius. For example, in one embodiment, the hot
pole is at 37.0 degrees Celsius, and the cold pole is at 35.5
degrees Celsius.
[0048] Transposing this thermal gradient .DELTA.T to the
thermoelectric energy converter system 204 with a small decrease in
thermal gradient .DELTA.T is desirable. As such, in some
embodiments, a thermally insulative insert is disposed between
first housing portion 202 and second housing portion 214. In some
embodiments, the thermally insulative insert is epoxy. In some
embodiments, the thermally insulative insert is conformed to first
portion 202 and second portion 214 and is hermetically sealed to
those portions.
[0049] Various methods for assembly fall within the present subject
matter. Various embodiments include connecting a thermoelectric
energy converter to a device housing, such that a hot pole of the
thermoelectric energy converter is connected to a first housing
portion, and a cold pole of the thermoelectric energy converter is
connected to a second housing portion, with the connected first and
second housing portions defining an interior volume in which the
thermoelectric energy converter is disposed. Additionally, various
embodiments include disposing a converter inside an interior volume
defined by a first housing portion and a second housing portion,
such that of the thermoelectric energy converter are respectively
connected to the first housing portion and the second housing
portion.
[0050] Some embodiments include packaging, in the interior volume,
a defibrillation capacitor powered by a battery. In some
embodiments, the battery is a primary battery. In additional
embodiments, the battery is a secondary battery.
[0051] Various embodiments include connecting the thermoelectric
energy converter to cardiac rhythm management electronics disposed
in the interior volume. For example, some embodiments include
connecting pacemaker electronics disposed in the interior volume to
the thermoelectric energy converter, such that the pacemaker
electronics are powered by the thermoelectric energy converter.
Some embodiments include connecting the thermoelectric energy
converter to neurostimulation electronics disposed in the interior
volume.
[0052] In various embodiments, therapy electronics (such as cardiac
rhythm management electronics, neurostimulation electronics, etc.)
and a secondary battery are connected to the thermoelectric energy
converter. In some of these embodiments, the secondary battery
powers the therapy electronics. In some embodiments, the
thermoelectric energy converter powers the therapy electronics. In
some embodiments, the thermoelectric energy converter powers the
secondary battery exclusively. Some embodiments include powering a
capacitor with the secondary battery. Capacitors contemplated by
the present subject matter include capacitors used as the primary
power source for providing shocks for defibrillation.
[0053] Some embodiments of the present subject matter include
methods of implanting a device having a thermoelectric energy
converter of the present subject matter in a patient such that the
first housing portion is positioned subcutaneously. Embodiments of
the present subject matter additionally include positioning a
housing submuscularly. The present subject matter includes
additional embodiments, however, which position the device in other
areas of the body.
[0054] FIG. 3 shows a side view of a self-powered device, according
to one embodiment of the present subject matter. In various
embodiments, a housing 310 includes a first portion 302, a second
portion 306, and an insert 304. Transposing thermal gradient
.DELTA.T.sub.2 to the thermoelectric energy converter system
decrease in thermal gradient .DELTA.T.sub.2 is desirable. As such,
in some embodiments, insert 304 is disposed between first housing
portion 302 and second housing portion 306.
[0055] In various embodiments, insert 304 is of a lower thermal
conductivity than the first portion 302. In additional embodiments,
the insert 304 is of a lower thermal conductivity than the second
portion 306. In some embodiments, insert 304 includes a thermally
insulative material. Some embodiments include a cured resin. In
some embodiments, the thermally insulative insert 304 is epoxy.
Various additional embodiments include other materials. In some
embodiments, the thermally insulative insert is conformed to first
portion 302 and second portion 306 and is hermetically sealed to
those portions.
[0056] Some embodiments do not include an insert, and instead rely
on a first portion of a housing and a second portion of a housing
each having a low thermal conductivity. For example, some
embodiments include a first portion of a housing and a second
portion of a housing, with the two portions assembled to one
another and defining an interior space. Within the interior space,
a thermoelectric energy conversion system extends between the first
and second housing portions, in various embodiments. The first and
second housing portions include a low conductivity material, in
various embodiments. But because, in various embodiments, the first
and second energy housings are thin, having a thickness of
approximately 0.012 inches, heat passes through them, traveling to
the thermoelectric energy conversion system. These embodiments
create a thermal gradient which is sufficient to power a
thermoelectric energy conversion device.
[0057] Various methods for assembly fall within the present subject
matter. Various embodiments include connecting a thermoelectric
energy converter to a device housing, such that a hot pole of the
thermoelectric energy converter is connected to a first housing
portion, and a cold pole of the thermoelectric energy converter is
connected to a second housing portion, with the connected first and
second housing portions defining an interior volume in which the
thermoelectric energy converter is disposed. Additionally, various
embodiments include disposing a converter inside an interior volume
defined by a first housing portion and a second housing portion,
such that of the thermoelectric energy converter are respectively
connected to the first housing portion and the second housing
portion.
[0058] Some embodiments include packaging, in the interior volume,
a defibrillation capacitor powered by a battery. In some
embodiments, the battery is a primary battery. In additional
embodiments, the battery is a secondary battery.
[0059] Various embodiments include connecting the thermoelectric
energy converter to cardiac rhythm management electronics disposed
in the interior volume. For example, some embodiments include
connecting pacemaker electronics disposed in the interior volume to
the thermoelectric energy converter, such that the pacemaker
electronics are powered by the thermoelectric energy converter.
[0060] In various embodiments, cardiac rhythm management
electronics and a secondary battery are connected to the
thermoelectric energy converter. In some of these embodiments, the
secondary battery powers the cardiac rhythm management electronics.
In some embodiments, the thermoelectric energy converter powers the
cardiac rhythm management electronics. In some embodiments, the
thermoelectric energy converter charges the secondary battery
exclusively. Also, some embodiments include powering a
defibrillation capacitor with the secondary battery.
[0061] FIG. 4 is a partial cross section of a self-powered
implantable device having a thermal shunt, according to one
embodiment of the present subject matter. Various embodiments of
the present subject matter include a first housing portion 414
which is thermally conductive and which has a first case opening.
Various embodiments include a second housing portion 402 which is
thermally conductive and which has a second case opening, with the
material defining the second case opening being hermetically sealed
to the material defining the first case opening, and with the first
housing portion and the second housing portion at least partially
defining an interior volume. The present subject matter includes
additional electronics 408 disposed in the interior volume, in
various embodiments. In some embodiments, the additional
electronics include cardiac rhythm management electronics.
[0062] Various embodiments additionally include a thermal shunt 412
disposed in the interior volume. The thermal shunt 412 is
constructed such that heat at first housing portion 414 is
conducted to the thermoelectric energy converter. As such, in
various embodiments, the thermal shunt is constructed from a
material having a high thermal conductivity. Materials contemplated
by the present subject matter include, but are not limited to,
copper, aluminum, silver, other materials and alloys thereof.
Another possible material is a carbon fiber composite having a
structure which is anisotropic and which demonstrates a high level
of thermal conductivity. An anisotropic material is beneficial as
it reduces the amount of energy conducted to an additional power
source 410 and additional electronics 408. In various embodiments,
the anisotropic material includes carbon fiber strands held in an
orientation by a cured resin. In some of these embodiments, epoxy
is the cured resin. Diamond powder is an additional material which
is suitable for construction of a shunt, according to various
embodiments of the present subject matter. Other materials which
are thermally conductive additionally fall within the present
scope. One embodiment uses a shunt which is a heat pipe.
[0063] Thermal shunt 412 is interconnected to other components in a
variety of ways. In some examples, the shunt is interconnected to
the first housing portion 414 using a weld. In additional examples,
the shunt is interconnected to the first housing portion 414 with a
thermal grease having a high thermal conductivity. In some
embodiments, an adhesive interconnects thermal shunt 412 to other
components. Additional mediums are also contemplated, including but
not limited to, epoxy and additional adhesives.
[0064] Also, various embodiments include a thermoelectric energy
converter 404 disposed in the interior volume and adjacent the
thermal shunt, the thermoelectric energy converter having a first
pole 416 and a second pole 418, with the first pole thermally
connected to the first housing portion, and the second pole
thermally connected to the shunt. In various embodiments, the first
pole 416 is a hot pole. In various embodiments, the second pole 418
is a cold pole. The thermoelectric energy converter 404, in various
embodiments, is film shaped. In some embodiments, the
thermoelectric energy converter 404 is a thin film device.
[0065] FIG. 5 shows a partial cross section side view of a
self-powered device, according to one embodiment of the present
subject matter. Various embodiments of the present subject matter
include a thermoelectric energy converter 504 which is in adjacent
a thermal shunt having multiple beams 506A, 506B, . . . , 506X. In
various embodiments, the multiple beams 506A, 506B, . . . , 506X
are configured for passage through various components 514 of a
self-powered device. In some embodiments, the multiple beams 506A,
506B, . . . , 506X pass through an additional power source. In some
of these embodiments, the multiple beams 506A, 506B, . . . , 506X
pass through a battery. In some of these embodiments, the multiple
beams 506A, 506B, . . . , 506X pass through a capacitor. In
additional embodiments, the multiple beams 506A, 506B, . . . , 506X
pass through electronics.
[0066] In various embodiments, the multiple beams 506A, 506B, . . .
, 506X are tubular columns of a conductive material. Materials
contemplated by the present subject matter include, but are not
limited to, copper, aluminum, silver, other materials and alloys
thereof. Other embodiments use additional shapes for the beams.
Additional embodiments include alternate materials such as an
anisotropic composite.
[0067] The illustration additionally shows a first case portion
502, a second case portion 512, an additional power source 510, and
additional electronics 508. The inclusion of the additional power
source 510 as illustrated is not limiting, as some embodiments of
the present subject matter integrate all additional power sources
into additional components 514. Also, the inclusion of the
additional electronics 508 as illustrated is not limiting, as some
embodiments of the present subject matter integrate all additional
electronics into additional components 514.
[0068] FIG. 6 shows a cross section of a thermoelectric energy
converter and additional components disposed in a shunt, according
to one embodiment of the present subject matter. The illustration
shows thermoelectric energy converter 602, shunt 606, and
additional components 604. In various embodiments, additional
components 604 include a battery. In some embodiments, additional
components 604 include a capacitor. Various embodiments dispose
electronics in shunt 606. Electronics include one or more of
pacemaker control circuits, cardioverter defibrillator circuits,
and other circuits. A combination of components listed herein
additionally are disposed in shunt 606, in various embodiments.
Components not listed herein, or combinations of components not
listed herein, may additionally be disposed in shunt 606. Some
embodiments include a solid shunt 606 having no components disposed
within. Some embodiments include a hollow shunt 606 having no
components disposed within.
[0069] In accordance with the requirements of components disposed
in shunt 606, shunt 606 includes feedthrough provisions, in various
embodiments. For example, in some battery embodiments, battery
electrodes are disposed in shunt 606. In some of these embodiments,
the anode of the battery is connected to a feedthrough, and the
cathode is connected to the shunt. In additional embodiments, the
cathode is connected to a feedthrough, and the anode is connected
to the shunt 606. Some embodiments include a feedthrough for the
battery anode and the capacitor cathode.
[0070] Additionally, in some capacitor embodiments, capacitor
electrodes are disposed in shunt 606. In some of these embodiments,
the anode of the capacitor is connected to a feedthrough, and the
cathode is connected to the shunt. In additional embodiments, the
cathode is connected to a feedthrough, and the anode is connected
to the shunt 606. Some embodiments include a feedthrough for the
capacitor anode and the capacitor cathode.
[0071] It is important to note that in some embodiments, an
electrolyte is in contact with the interior of the shunt 606, and
functions as part of the components housed in the shunt 606. For
example, in some embodiments, a capacitor using the shunt 606 as a
housing includes a thermally conductive electrolyte which further
benefits the heat conducting properties of the shunt 606.
[0072] FIG. 7 shows a cross section of a shunt and a thermoelectric
energy converter, according to one embodiment of the present
subject matter. In various embodiments, a thermoelectric energy
converter 704 is disposed between a first shunt 702 and a second
shunt 706. The first shunt 702 and the second shunt 706 are
respectively adjacent first and second portions of a self-powered
device housing, in various embodiments. First shunt 702 and second
shunt 706 are solid in some embodiments. Additional embodiments
include one or both of the first shunt 702 and the second 706 in a
hollow configuration.
[0073] FIG. 8 is cross section or a self-powered device showing
thermal gradients, according to one embodiment of the present
subject matter. The illustration shows a thermal representation of
the temperature at a first housing portion 804, a thermoelectric
device 808, a shunt 806, a second housing portion 812, an
additional power source 810, and additional electronics 802.
Pictured is temperature gradient .DELTA.T.sub.2, which in the
illustrated example represents a temperature drop of approximately
0.9 degrees Celsius across the thermoelectric energy converter.
Such a temperature gradient is sufficient to provide power of
around forty microwatts to one or both of the additional
electronics 802 and the additional power source 810. Other
temperature gradients .DELTA.T.sub.2 and power outputs fall within
the present scope. Applications which could produce .DELTA.T.sub.2
include implantation below a patient's skin, with the first case
portion 804 positioned subcutaneously. Embodiments of the present
subject matter additionally include positioning a housing
submuscularly. These power production examples are evinced in some
of the configurations contemplated by the present subject matter,
but are not intended to be limiting of the range of configurations
contemplated by the present subject matter. Additionally, the
thermal gradients provided herein, and their relationship to power
production, are those of example embodiments which are illustrative
of the present subject matter, but not demonstrative of the entire
range of configurations contemplated by the present subject
matter.
[0074] Thermoelectric generators convert heat to electrical power.
This electrical power typically has current in the milliampere (mA)
range and voltage in the microvolt (.mu.V) range. The voltage
required by a typical implantable medical device is several orders
of magnitude larger. Additionally, excess energy can be stored for
future use, but most energy storage systems require voltages higher
than what is generated by a thermoelectric generator. The present
subject matter provides an apparatus and method for converting the
output of a thermoelectric generator to voltages compatible with an
implantable medical device.
[0075] FIG. 9 shows a circuit for converting power from a
thermoelectric energy converter, according to one embodiment of the
present subject matter. To provide power in a form compatible with
various loads, an energy conversion circuit is provided. In various
embodiments, the electronics of the present subject matter are
adapted to control the conduction of energy between the
thermoelectric energy converter and a power source. In some
embodiments, these electronics control the transmission of energy
to a secondary battery. In additional embodiments, the electronics
control the transmission of energy between a battery and a
defibrillation capacitor. In some embodiments, the thermoelectric
energy converter powers a defibrillation capacitor concurrent with
a battery.
[0076] FIG. 9 illustrates a schematic diagram of an apparatus for
converting power from a thermoelectric energy converter, according
to one embodiment of the present subject matter. The apparatus 900
includes an input terminal 902 for receiving an input voltage
generated by a thermoelectric energy converter 920 and a charging
inductor 904 connected in series with the input terminal. The
apparatus also includes a switching Field Effect Transistor (FET,
906) connected to the inductor. A capacitor 908 is connected to the
FET and the input terminal via a diode 910. According to various
embodiments, the FET 906 is switched with a frequency and duty
cycle such that a voltage level at the output terminal 912 is
compatible with an implantable medical device. Implantable medical
devices refer to devices used for in situ sensing and/or therapy
delivery. Examples include, but are not limited to, chronically
implanted devices such as pacemakers, cardioverters/defibrillators,
and neurostimulators.
[0077] The capacitor 908 has a capacitance of 1 .mu.F, according to
an embodiment. According to various embodiments, the charging
inductor 904 includes a hand-wrapped wire inductor. The charging
inductor 904 includes 22 turns of 34 gauge wire, according to an
embodiment. Other types and sizes of inductors are within the scope
of this disclosure. In various embodiments, the apparatus provides
power efficiency from the input terminal 902 to the output terminal
912 of 20 to 30%. The FET 906 is switched with a frequency of 10
kHz, according to one embodiment. According to various embodiments,
the FET 906 is switched using a closed loop feedback system that
controls the frequency and duty cycle based on an observed voltage
level at the output terminal 912. The FET is switched with a duty
cycle of at least 90%, according to various embodiments.
[0078] The apparatus functions as an inductive boost circuit. The
depicted implementation minimizes the number of circuit elements,
and further reduces the need for customized circuit elements. The
circuit elements are appropriate for inclusion on an
application-specific integrated circuit (ASIC). The low part count
allows for easy implementation and minimizes package size. The
resistance of the inductor and FET are minimized to increase
efficiency of the converter circuit.
[0079] The switching FET is selected to have a low resistance when
switched "on". According to an embodiment, the FET has an "on"
resistance of approximately 40 ohms. The inductor is selected to
have a low resistance as well, to improve the efficiency of the
apparatus. The apparatus takes as an input the relatively low
voltage from the thermoelectric generator (8-100 .mu.V, according
to various embodiments) and builds the voltage on the capacitor.
The voltage level on the capacitor, or output voltage, is
determined by the loading of the output circuit, the heat flux
across the thermoelectric generator, the efficiency of the
thermoelectric generator, and the pulse frequency and duty cycle of
the switching FET. The frequency and duty cycle can by controlled
using a closed loop system. According to an embodiment, the
frequency and duty cycle are controlled using logic. The frequency
and duty cycle are controlled using pulse-width modulation,
according to an embodiment. An oscillating supply 914 connected to
the gate of the FET 906 via logic 916 can be used to set and adjust
frequency and duty cycle. In an embodiment, the oscillating supply
is controlled using feedback from an observed output voltage.
[0080] The FET 906 includes circuit element model IRF7530, for
example, in an embodiment. The diode 910 includes circuit element
model 1N4148, for example, in an embodiment. Other circuit elements
having the similar characteristics can be used without departing
from the scope of the disclosure.
[0081] Some embodiments of the present subject matter include
methods of implanting a device having a thermoelectric energy
converter of the present subject matter in a patient such that the
first housing portion is positioned subcutaneously. Embodiments of
the present subject matter additionally include positioning a
housing submuscularly. Some of these embodiments position the
housing of between the pectoral muscle and the skin. The present
subject matter includes additional embodiments, however, which
position the device in other areas of the body.
[0082] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement which is calculated to achieve the
same purpose may be substituted for the specific embodiment shown.
This application is intended to cover adaptations or variations of
the present subject matter. It is to be understood that the above
description is intended to be illustrative, and not restrictive.
Combinations of the above embodiments, and other embodiments will
be apparent to those of skill in the art upon reviewing the above
description. The scope of the present subject matter should be
determined with reference to the appended claims, along with the
full scope of equivalents to which such claims are entitled.
* * * * *